MICROPROCESSOR CONTROLLED AIR DATA COMPUTER FOR GLIDERS. RELIABLE AND EXPANDABLE BY USING MOST ADVANCED COMPUTER TECHNOLOGY, COMPACT SYSTEM SAVING PANEL SPACE: ONLY TWO UNITS,
Variometer, speed command, relative vario without altitude errors; continuous computation and indication of average climb rate; distance to go computer with pre-selectable waypoints; final glide computer; wind calculator; statistics computer; automatic switching between "vario" and "speed command" modes; for every type of glider (only set best L/D and wing loading of your plane}: microprocessor controlled - prepared for improvements and expansions.
The variometer uses a thermistor bridge with very low zero offset; all errors related to this type of sensor are eliminated by the microprocessor: the signal is linearized and corrected for altitude and temperature by using additional altitude and temperature sensors within the computer housing.
A TEC probe is necessary for total energy compensation.
| 1/0 | = | (S) | on/off switch |
| START | = | (S) | distance, time and statistics are counting if glider is airborne |
| STOP | = | distance, time, statistics are staying unchanged | |
| ±1/±10 | = | (M) | to change the number marked by the cursor (cursor = line under mc, D, W, ...) |
| <=> | = | (M) | cursor left / right |
| up/down | = | (M) | page advance / back |
| - R - | = | (M) | reset (clear) time, statistics and waypoints (press both momentary switches at the same time) |
| Speaker | = | (M) | audio volume increase / decrease (different for "vario" and "speed command" mode) |
| Up Arrow | = | (S) | mode selector "variometer" / "automatic" / "speed command" |
The momentary switches can be moved up or down. All momentary switches have "repeating function"; for example; holding the "+l"-switch down will increase the selected number by +1 automatically every 3 sec.
After turning on power there are six numbers shown on the LCD-display:
1.5mc 078D -10W 0.8M 2.95H 3:45 |
The cursor (line) under "mc" shows that the MacCready value can be changed by using the "1/10"-switch. To change the distance the cursor must be moved to "D" by pushing the "cursor right/left"-switch once. Then the distance can be set using the "1/10"-switch. Pushing the "cursor right/left"-switch again moves the cursor to the wind. Moving the cursor switch upwards twice brings the cursor back to "mc". The cursor will return automatically to the "mc" position if there was no action at the momentary switches for more than 10 sec.
During "speed command" there will be displayed the average netto climb instead of average climb (marked by "n" instead of "M").
The next set of numbers (page) will be shown after pushing the "page advance"-switch once. Again all numbers can be changed by using the cursor switch and the "1/10"-switch.
35L 40E 0.15F A=1 R=0 |
The next page shows battery voltage and outside air temperature. Also there is the possibility to preset up to nine waypoints,
12.6Volt 21.3 C WP1: 132km |
The fourth page shows a set of statistic values to evaluate one flight:
03:45 0323d 086v 08.1h 1.4m 042% |
Moving the page switch upwards returns to the first page with the cursor under "mc"
All datas within the computer will be stored even when power is turned off. So all inputs (like L/D and others) will stay. The statistics too are saved and can be evaluated later when there is time to do this.
When the battery voltage is less than 11.0 volts the warning "batt" is shown on display page 1 in the right lower corner (instead of the time). When in switch position "STOP" then there will be shown "stop" in the right lower corner on page 1 to remind of the fact that distance and time are not counting.
At a known position the distance is set. After some time the distance shown can be adjusted by changing the wind component. The new wind setting is equal to the calculated wind component (adaptive wind calculator).
The switching between both modes is normally controlled by a magnet actuated switch mounted to the flap lever. Gliders without flaps can use the internal automatic where switching is a function of climb and speed signals: when the rate of climb is greater than the MacCready setting then "vario" is activated; if the rate of climb is less and the air speed is greater than a reference speed then the mode is changed to "speed command". The reference speed is a function of the selected wing loading and is about 100km/h with 32kp/m².
Similar to other speed command computers the round indicator of the SR 820 normally shows the speed error during "speed command". But if desired it is also possible to show the relative vario signal instead. This shows at any speed which climb rate could be achieved when circling. The additional sink rate due to higher speeds is eliminated. The audio is still connected to the speed command signal and will further provide the "faster" or "slower" commands.
Up to nine waypoints (partial distances) can be preprogrammed before takeoff. The first waypoint will be transferred to the distance when switching from STOP to START. Another short movement of the switch to STOP and back to START (at the turnpoint for instance) brings the next waypoint into the distance counter.
The audio volume is set by the switch "audio increase/decrease"; there are two different settings for "vario" and "speed command". During "vario" the computer produces a staircase tone, which shows very impressively an increasing or decreasing climb rate. During sink the staircase tone is interrupted. During "speed command" there is a speed dependent quiet zone around zero with adjacent rough tone steps. So it is relatively quiet in the cockpit during "speed command". The audio so shows a clear distinction between the "vario" and the "speed command" mode.
The SR 820 computer must be connected to a TEC probe which can be used at the same time for another variometer. A TEC probe normally produces a very good variometer signal without critical adjustments at the computer end without drilling new static holes into the glider fuselage. On the other hand the use of a TEC probe allows a more insensitive technology compared to electronic compensation. So the influence of humidity and radio interference is reduced.
If desired the computer can be prepared to allow the connection of two potentiometers which are mounted outside of the computer to the instrument panel. Then both MacCready and wind setting can be changed directly on two scales (each 40mm wide, 32mm high). The cursor on page 1 is now positioned under "D" so that the distance can be changed directly with the "1/10"-switches. If the potentiometer plug is disconnected then the standard function of the computer is automatically reentered.
While the standard program version "A" (as described~ above) is designed for a handling as simple as possible and still has all important functions, there are other program versions with more functions. It should be noted that these additional functions require additional inputs and will make the use of the computer more pretentious. The following versions contain all functions of the version "A"; the potentiometer option is available too.
This version allows switching the compensation from TEC probe to electronic compensation after failure of the probe (due to water for instance). A pneumatic switch must be provided to switch the computer from probe to static pressure. This emergency compensation performs not as well as probe compensation but is sufficient for circling. In addition to this function this version has the possibility to set a airspeed correction factor for more precise distance measuring.
The version "E" is especially useful for motorized gliders. When the engine is running the variometer is switched from TEC probe to static pressure by the pneumatic switch which is already installed; after switching the computer to electronic TEC the variometer is compensated again. After turning off the engine the compensation is switched back to the better performing TEC probe.
This version contains all functions of version "E". Besides this a vertical acceleration sensor is integrated into the computer. Then there are following new functions: adjustable low speed audio warning and programmable flap position computer. Activation of the low speed warning is done by setting a typical speed limit (straight and level, as for wing loading 52kp/m²); when flying too slow the vario tone gets a chirp; the minimum speed is automatically recalculated using wing loading setting and vertical acceleration. This function works only during "vario". The flap computer requires input of up to four speed limits related to a wing loading of 32kp/m². Now the computer shows in every flight condition the correct flap position due to airspeed, wing loading setting and acceleration. The recommended flap position is shown on display page 1 (instead of time) in five steps: -2 -1 0 +1 +2 . Deleting the inputs turns of the flap computer and the display page 1 shows the time again.
All program versions are also available in other than "m/s. km, km/h" units. Already prepared are "knots, statute miles, feet" (USA) and "knots. km. feet" (Australia].
New program versions are continuously developed and tested, the programs in use will be improved. All gliding computers SR 820 are prepared for later changes and expansions. So your SR 820 computer can be the most advanced model for many years.
WARRANTY: 2 Years
DIPL.ING. PETER ZANDER. WOLFFRATSHAUSER STR.